Seriously, some doctors are friggen clueless. Your best hope lies with other people who experience that. I get that from time to time, usually after I wake up or exercise hard. Now that I think about it, I've been getting it intermittently since highschool. The symptoms you described are EXACTLY like the ones I experience. I tried the holding nose and blowing slightly even before I read your post, and I had the same effects: that is, I heard about 100% louder/better for the time I'm increasing pressure in my nose (wihch possibly is balancing it with part of the ear that's overpressured). But, the moment I let got of my nose, I go back to hearing like 50%. For me, what helps is:
1) yawning, both real yawning and fake yawning with jaws moving and wide open. 2) sometimes holding both my nose and blowing helps, but not always. You have to feel for it. Sometimes I can feel that the pressure building up in my nasal cavity is about to burst out through the ear canal, thus restoring the proper pressure level to the ear. Sometimes, it's not going to happen, so I just give up because I don't want to damage my ears. 3) Sometimes, I go to extremes by driving to a local area where there's a large veritical geographical gap. In english, that means I drive to a place where it goes downhill for 5 mins or so. At the bottom of the drive, I yawn or do the holding nose trick and it sometimes work. That's probably because the air pressure difference between the top of the hill and bottom of the hill is such that it's more helpful than staying home. 4) Ignore it and it usually relieves itself. 5) Some people mention eating spicy stuff to make you have a running nose. I've never tried that.
Sometimes I wonder if I can put a suction cup or something over my ear to see if that helps. But who knows.